The validity of consumer-level, activity monitors in healthy adults worn in free-living conditions: a cross-sectional study

TLDR

Technological advances have created a burgeoning industry of accelerometer‑based wearable activity monitors aimed at consumers. The study aimed to assess the convergent validity of seven consumer‑level accelerometer‑based activity monitors against research‑grade devices in healthy adults during free‑living conditions. Participants wore the monitors for 48 hours while going about their daily lives in free‑living conditions. The monitors demonstrated strong validity for step count and sleep duration, moderate validity for total daily energy expenditure and moderate‑to‑strong validity for moderate‑to‑vigorous physical activity, with Fitbit One, Fitbit Zip and Withings Pulse performing best and median absolute differences modest for steps/sleep (<10 %), moderate for TDEE (<30 %) and large for MVPA (26–298 %).

Abstract

Technological advances have seen a burgeoning industry for accelerometer-based wearable activity monitors targeted at the consumer market. The purpose of this study was to determine the convergent validity of a selection of consumer-level accelerometer-based activity monitors.21 healthy adults wore seven consumer-level activity monitors (Fitbit One, Fitbit Zip, Jawbone UP, Misfit Shine, Nike Fuelband, Striiv Smart Pedometer and Withings Pulse) and two research-grade accelerometers/multi-sensor devices (BodyMedia SenseWear, and ActiGraph GT3X+) for 48-hours. Participants went about their daily life in free-living conditions during data collection. The validity of the consumer-level activity monitors relative to the research devices for step count, moderate to vigorous physical activity (MVPA), sleep and total daily energy expenditure (TDEE) was quantified using Bland-Altman analysis, median absolute difference and Pearson's correlation.All consumer-level activity monitors correlated strongly (r > 0.8) with research-grade devices for step count and sleep time, but only moderately-to-strongly for TDEE (r = 0.74-0.81) and MVPA (r = 0.52-0.91). Median absolute differences were generally modest for sleep and steps (<10% of research device mean values for the majority of devices) moderate for TDEE (<30% of research device mean values), and large for MVPA (26-298%). Across the constructs examined, the Fitbit One, Fitbit Zip and Withings Pulse performed most strongly.In free-living conditions, the consumer-level activity monitors showed strong validity for the measurement of steps and sleep duration, and moderate valid for measurement of TDEE and MVPA. Validity for each construct ranged widely between devices, with the Fitbit One, Fitbit Zip and Withings Pulse being the strongest performers.